1. Field of the Invention
This invention relates generally to the field of sterilizing and cleaning tubular structures including long, narrow, tubular structures. In particular, it relates to a device and method for cleaning and sterilizing medical devices with lumens.
2. Description of the Related Art
Many tubular structures, in particular flexible fiber endoscopes, define long tortuous lumens. These lumens are typically from about 1 m to about 4 m long with inside diameters from about 0.5 mm to about 6 mm and frequently contain crevices, bends, connections, restrictions, and irregularities. These instruments are frequently used in diagnostic medicine, requiring penetration into the human body or other contact with the human bloodstream. It is, therefore, desirable that they are cleaned, rinsed, sterilized, disinfected, or otherwise treated with fluid chemical disinfectants or sterilants to prevent the cross contamination and transmission of pathogenic organisms from patient to patient. In order for fluid chemical sterilization to be effective, the chemical must reach all internal and external surfaces. Efficaciousness, therefore, is severely limited by the inherent irregularities present in the long, narrow, lumens of flexible fiber endoscopes making effective cleaning and sterilization difficult.
Consistently and quickly cleaning, disinfecting, and sterilizing medical devices is an important part of providing quality healthcare. Failure to consistently clean and sterilize medical instruments leads to unwanted transmission of bacteria, viruses, and other organisms to and from patients. Improper handling of medical instruments allows unwanted organisms access inside the body where they may cause infection and disease.
Although the terms xe2x80x9csterilizationxe2x80x9d and xe2x80x9cdisinfectionxe2x80x9d are sometimes used imprecisely, the medical industry and regulatory agencies have more precisely defined the following terms including subdividing disinfection into high, intermediate, and low level disinfection.
Sterilization is generally defined as the destruction or elimination of all microbial life forms. Operationally, a sterilizing process is one that destroys all microbes on a device that has been contaminated with 106 bacterial endospores.
High level disinfection is generally defined as the destruction or elimination of all microbial life forms except microbial spores. High level disinfectants however, must show a capability of destroying bacterial spores over an extended period of time.
Intermediate disinfection is generally defined as the destruction of all microbial life forms except bacterial spores and some viruses. However, intermediate disinfection requires the destruction or elimination of Mycobacterium tuberculosis var. bovis, which is a relatively difficult bacterium to destroy.
Low level disinfection is generally defined as the destruction of vegetative forms of bacteria (such as salmonellae and staphylococci), most fungi, medium sized or lipid containing viruses (such as Herpes simplex virus, hepatitis B virus, and HIV), but not bacterial endospores, mycobacteria, or small or non-lipid viruses (such as poliovirus and rhinovirus).
The level of disinfection or sterilization desired for a particular piece of equipment generally depends on the degree of exposure the equipment poses to the patient. For example, sterilization is generally necessary for equipment that is introduced directly into the human body, either in contact with the blood stream, or in contact with normally sterile areas of the body. High level disinfection is generally required for equipment that contacts mucus membranes, but does not penetrate bodily surfaces. Low and intermediate disinfection is generally required for equipment that contacts unbroken skin.
Endoscopes, which are used to probe internal passages of the body, are an exception to the general rule of sterilizing equipment that is introduced directly into the human body. Ideally, all endoscopes should be cleaned and sterilized between uses. However, due to their delicate optical equipment, endoscopes remain an exception to the sterilization rule. The delicate optical equipment and lenses in these devices do not allow conventional methods of sterilization such as autoclaving, ethylene oxide gassing, or soaking for several hours in liquid sterilants. Autoclaving requires high temperatures for sterilization, which damages the optical lenses of the endoscopes. Ethylene oxide gas equipment is expensive and requires several hours to complete the sterilization and degassing process. Repeated soaking in liquid sterilants may also damage some endoscopes. In addition, the high cost of these specialized pieces of equipment demands efficient utilization of the instruments, requiring use of the same endoscope on as many patients in as little time as feasible. Therefore, soaking in liquid sterilants or sterilization by ethylene oxide gas is not economically feasible because of the long time period required. The demand for rapid reuse results in pressure to shorten or eliminate cleaning, disinfection, and sterilization practices. As a compromise to all of these considerations, high level disinfection for endoscopes is conventionally accepted in lieu of sterilization.
Although high level disinfection has been conventionally acceptable, it does not provide the level of safety of sterilization. The conventional rationale for accepting the reduced level of safety is that endoscopes contact mucus membrane and do not provide access to the blood stream. However, endoscopes are routinely used to find lesions in mucus membrane areas that may provide access to the blood stream. In addition, many endoscopes provide biopsy forceps that are miniature scalpels used to cut biopsy samples from the mucus membrane tissue. These common practices provide access to the bloodstream and a potential pathway for unwanted organisms to access all parts of the body. In addition to providing a direct path to the bloodstream, many endoscopes such as duodenoscopes are used in normally sterile parts of the body. Introducing contaminated equipment into these areas has been shown to cause infection.
The lumens of medical devices have conventionally been difficult to clean, disinfect, and sterilize. Some larger lumens may be cleaned with brushes. However, lumens that are too small for brushes are generally limited to cleaning by flushing with fluids such as water or air. As noted previously, the lumens also contain crevices, bends, connections, restrictions, and irregularities that restrict flow and hold residual material making cleaning difficult. Before a piece of equipment is disinfected or sterilized, it is preferably first cleaned. Failure to completely clean residual material from the equipment potentially leaves microorganisms within and beneath the residual material not easily accessible to the disinfectant or sterilant.
Some conventional devices have used special attachments or caps to direct flow into different passages of endoscopes. However, these attachments create additional attachment points. The unexposed surfaces between the attachment and the medical device may not receive complete cleaning or sterilization.
Typically, conventional devices and methods of cleaning have used uni-directional flow to clean long narrow devices with lumens. It is believed that irregularities and restrictions in the passages create air pockets or sheltered areas along the passages. For example, as the fluid flows around corners, the fluid tends to flow to the outside of the corner, leaving an air pocket or undisturbed liquid or material on the inside edge. Fluid flow is also reduced on the downstream side of any restriction.
Some devices, such as those disclosed in Ishii U.S. Pat. No. 4,526,623, use suction from a syringe to draw residual fluid in the lumens or to draw fluid from an additional fluid container. However, the use of suction may collapse lumens, introduce additional air pockets in the lumen, and create the need for additional attachments. Suction may also require the use of check valves to properly control the removal of fluid and reduce the amount of air introduced into the medical device. Check valves may also reduce or eliminate complete removal of the fluid. Cleaning by suction only removes liquid from multiple lumens until one lumen contains air. Once a single lumen contains air, only air is drawn through the device because air flows more easily than liquid. The relative differences in the size of the lumens would also cause certain lumens to drain more quickly, leaving liquid in the remaining lumens. Lastly, the syringe method and device of Ishii is not easily automated.
Sterilization methods have also included immersion or soaking of medical devices in liquid sterilant. Sterilization by soaking typically requires several hours and air bubbles may become trapped inside the lumens, causing inconsistent results.
A new and useful device and method is needed that overcomes the problems associated with conventional methods of cleaning and sterilizing tubular structures, including long, narrow, tubular structures, particularly medical devices with lumens, by providing a device and method that provides a reverse flow through the tubular structures.
It is an object of the reverse flow cleaning and sterilizing device and method in accordance with the present invention to solve the problems outlined above that have heretofore inhibited the successful cleaning and sterilization of tubular structures, in particular, long, narrow, tubular structures.
More particularly, the apparatus and method of the reverse flow cleaning and sterilizing device in accordance with the present invention provides for the cleaning and sterilization of medical devices with lumens, particularly endoscope lumens.
The unique sterilization and cleaning device in accordance with the present invention broadly includes a first valve and a second valve. The first and second valves are each in fluid communication with a fluid supply at a positive pressure. The first valve is in fluid communication with a first tubular structure having a proximal end and a distal end with the first valve in fluid communication with the proximal end. The second valve is in fluid communication with a second tubular structure having a proximal and a distal end with the second valve in fluid communication with the proximal end. The first tubular structure is in fluid communication with the second tubular structure. The first and second valves selectively switch between a first position and a second position. The first position causes a first fluid flow path and the second position causes a second fluid flow path. At least part of the second fluid flow path is opposite the first fluid flow path. In the first position the first valve is open to the fluid supply and the second valve is closed to the fluid supply. In the second position the second valve is open to the fluid supply and the first valve is closed to the fluid supply.
The device may also provide that either both fluid flow paths start at one end of a medical device or one fluid flow path may start in a control head or center of the medical device.
The device may also provide that the distal end of at least one of the tubular structures is open to a drain at about atmospheric pressure.
The device may also provide that in the first position the second valve is open to a drain line and in the second position the first valve is open to a drain line.
The device may also provide that the fluid supply has a flow volume from about 100 ml/min to about 1400 ml/min and a flow velocity from about 50 cm/sec to about 500 cm/sec and a pressure below about 20 psi for about 1 minute to about 20 minutes.
The device may also provide a third and a fourth valve, a third and a fourth tubular structure, and a third and a fourth position.
The device may also be used in an automatic reprocessing device so that a central processor controls positioning of the valves.
The apparatus and method in accordance with the present invention provides both a method of sterilization of tubular structures and a method of cleaning the lumens of a medical device.
The sterilization method broadly includes the sterilization of the interior of a tubular structure comprising: a) providing a tubular structure, b) providing a sterilizing fluid c) causing the sterilizing fluid to flow at a positive pressure through the tubular structure in a first fluid flow path, and d) causing the sterilizing fluid to reverse flow at a positive pressure through the tubular structure in a second fluid flow path, so that at least part of the second fluid flow path is opposite the first fluid flow path.
The sterilization method may also include providing the sterilizing fluid at a temperature from about 20 degrees C. to about 50 degrees C. and from about 1 minute to about 20 minutes.
The sterilization method may also include providing a tubular structure having a diameter equal to or less than about 6 mm and the flowing and the reverse flowing have a flow velocity from about 50 cm/second to about 500 cm/second, a flow volume from about 100 ml/min to about 1400 ml/min, and a pressure below about 20 psi.
The sterilization method may also include starting the first fluid flow path and starting the second fluid flow path in one end of a medical device.
The device may also provide that one fluid flow path may start in a control head or other attachment point of the medical device.
The sterilization method may also include providing the device of the present invention.
The sterilization method may also include controlling the flowing and the reverse flowing by a central processor.
The present invention may also include a method of cleaning a medical device with lumens. The cleaning method broadly includes a method of cleaning the lumens of a medical device including a) providing a medical device with a first lumen and a second lumen, each lumen having a proximal end and a distal end, the first lumen in fluid communication with the second lumen, and the second end of at least one of the lumens open to a drain at about atmospheric pressure; b) providing a cleaning fluid; c) causing the cleaning fluid to flow at a positive pressure through the lumens in a first fluid flow path starting at the proximal end of the first lumen; and d) causing the cleaning fluid to reverse flow at a positive pressure through the lumens in a second fluid flow path starting at the proximal end of the second lumen, such that at least part of the second fluid flow path is opposite the first fluid flow path.
The cleaning method may also include providing a medical device with the first end of each lumen located in the same end of the medical device.
The cleaning method may also provide that either both fluid flow paths start at one end of a medical device or one fluid flow path may start in a control head or other attachment point of the medical device.
The cleaning method may also include draining the first fluid flow path through the proximal end of the second lumen and draining the second fluid flow path through the proximal end of the first lumen.
The cleaning method may also include providing the flowing and the reverse flowing at a flow velocity of from about 50 cm/sec to about 500 cm/sec, a flow volume from about 100 ml/min to about 1400 ml/min, and a pressure below about 20 psi.
The cleaning method may also include providing the device of the present invention.
The cleaning method may also provide controlling the flowing and the reverse flowing by a central processor.
One advantage of the present invention is improved sterilization. The present invention provides better application of the fluid to all parts of the interior of tubular structures. Improved application of the fluid to the interior of the tubular structure results in faster and more consistent sterilization.
Another advantage is that air pockets are consistently removed. The present invention improves sterilization and cleaning by providing better application of fluid by consistently removing air pockets from the interior of the tubular structures. Flowing and reverse flowing at a positive pressure provides consistent removal of air pockets. Soaking or holding fluid in the tubular structures does not consistently remove air pockets resulting in inconsistent cleaning and sterilization.
Another advantage is that the fluid obtains improved access to cracks, crevices, and restrictions. Flowing and reverse flowing at a positive pressure forces fluid into cracks, crevices, and restrictions from more than one direction. Flowing from one direction or flowing at a negative pressure does not force fluid into the cracks and crevices, especially downstream of a restriction, causing inconsistent sterilization and cleaning.
Another advantage is that residual liquids and materials remaining in the lumens are more adequately displaced with fluid. Liquid, such as left over rinse water may not be completely displaced using an uni-directional flow pattern. As a result, the chemicals (active ingredients) in the fluid must diffuse into the rinse water before sterilization may occur. The present invention provides better displacement of residual materials and liquids providing faster and more consistent sterilization and cleaning.
Another advantage is that soaking is not required. The present invention is not limited by the use of large volumes of sterilizing fluid needed to immerse the entire tubular structure, saving sterilization fluid.
Another advantage is that sterilization can be accomplished more quickly. Long soaking times of hours required for immersion sterilization may be reduced to about minutes for the present invention. Quicker sterilization results in better utilization of medical equipment.
Another advantage is that sterilization can be accomplished more consistently. Flowing sterilizing fluid from more than one direction and forcing the sterilizing fluid into cracks and crevices with positive pressure reaches the interior surfaces of tubular structures more consistently. More consistent application of the sterilizing fluid to the interior surfaces provides more consistent sterilization.
Another advantage is that the present invention can be attached to the supply ports of the endoscope. The present invention may be attached to one end of a medical device such as an endoscope without any attachments to the distal end or insertion section of the medical device. Other methods using suction pressure require the attachment of a fluid source in addition to the suction source requiring additional attachments. A device that connects to one end of the medical device provides an easier and more centralized attachment and eliminates the need for additional attachments.
Another advantage is that the present invention provides an alternative method of attachment to the air/water channel, particularly if the device does not have a gas or CO2 channel. The present invention may provide for attachment to the air/water channel at the air/water control cylinder.
Another advantage is that the present invention reduces the number of attachments that cause additional contamination points. Each additional attachment creates an area between the attachment and the medical device that is difficult to reach with fluid. The more attachments the greater the inconsistency of cleaning and sterilization.
Another advantage is that the present invention uses positive pressure flow. In addition to the improved penetration capabilities previously described, positive pressure flow is easier to provide. Positive pressure provides a greater range of pressures and can be more easily provided through a greater variety of positive pressure pumps. Positive pressure flow provides both the pressure source and the fluid source at one location, simplifying connections and automation. Positive pressure is also safer because contaminates cannot be drawn into the device through leaks in the system.
Another advantage of the present invention is that it may be operated at temperatures less than 50 degrees C. Operating at temperatures below 50 degrees C. prolongs the life of medical devices and reduces burn hazards.
Another advantage is that the present invention may be easily automated. The use of valves controlled by a central processor may be easily automated, particularly in an automatic reprocessing device. The elimination of manually operated equipment and methods such as syringes provides for automation.
These and other objects and advantages of the present invention will become apparent during the course of the following detailed description and appended claims. The invention may best be understood with reference to the accompanying drawings, wherein an illustrative embodiment is shown.